Mid-Drivers and Crossovers, Point me in a Direction?...

Discussion in 'Amps [BG]' started by Count Bassie, Dec 12, 2012.


  1. Count Bassie

    Count Bassie Supporting Member

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    I'm going to 'break the law' for some of you, and plan to put a mid-driver in my Hartke VX-215 cab. The tweeter is gone south, and good riddance I say. But now it's a tad 'dark', and needs a little snap.

    I'm in need of some crossover education and advice... I'm using SWR 400 and 500 watt heads (one at a time!), and it appears many of these 6.5" or so woofers need around 100 watts to 'go'. Here's one I looked at: http://www.usspeaker.com/alpha6cbmra-1.htm

    So I need to regulate how much juice the little guy gets, and to send it a reasonable x-over point, so that the 15s will still get to do their job adequately.

    Getting pointed in the right direction would be greatly appreciated! Many thanks!

    ...and for those of you who would steer me to other, better ideas (fEARful, Dually, etc- which are fine ideas), I just don't have the time or means to get into a project like that now. I got this on the cheap, and want to make the most of it...
     
  2. Codger

    Codger Supporting Member

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    How about an Eminence passive? PXB2:1K6 or PXB2:800. These are eight ohm, 400W 2-way, 18dB/oct on the high-pass, 12db on the low. Its the easiest way without measuring parameters and designing and all that... stuff.

    Edit: Oops - that cab is 4 ohm. Oh well.
     
  3. Count Bassie

    Count Bassie Supporting Member

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    I still have to do some reading, but there's the driver and there's the x-over. How does wattage get regulated for that driver? How do you deal with ohmage? The cab is already 4 ohms... adding another driver doesn't lower the resistance?

    Etc... I'm not in a hurry. Will do reading over the weekend...
     
  4. AstroSonic

    AstroSonic Supporting Member

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    If there is a tweeter crossover already in the cab and if the tweeter is marked for impedance (like 4 or 8 ohm), the easiest thing to do is replace the tweeter with a better one. You might also want to ad an L-pad to adjust the amount of power the tweeter receives. This is the safest way to go.

    Let us know what you find in that cab.

    OTOH, it's not unlikely that the 15's are being run wide open (no crossover/natural rolloff), and that the tweeter was an inexpensive piezoelectric unit and was run with no crossover (it can be done because they have a very high impedance below 3-4 kHz that strongly limits amplifier power- kind of a 'natural' crossover). In that case (and at a minimum) you will need a high pass crossover for the tweeter (letting the 15's run wide open) and an appropriate driver. Not ideal, but this will quite reliably add some "a little snap".

    Also, I think it quite possible that the 8 ohm Alpha 6 will not keep up (won't be loud enough) with the two 8 ohm 15's wired in parallel for 4 ohms.

    Ask a simple question... :>))
     
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  6. Count Bassie

    Count Bassie Supporting Member

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    Yeah I'll watch for you now... :D

    Interesting, the Alpha not keeping up- maybe why the fEARful 15/15 6/6 has two...
     
  7. Count Bassie

    Count Bassie Supporting Member

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    Hey mods- should this get moved to "DIY"?
     
  8. CL400Peavey

    CL400Peavey Supporting Member

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    The 15/6 and the 1515/66 both use 18sound mid drivers. The 12/6's are designed with the Alphalites in mind.
     
  9. Count Bassie

    Count Bassie Supporting Member

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    I'm just trying to do a simple idea here. Need a mid driver and suitable crossover (say around 1 or so KHz?), keep the 15s running at full-throttle.

    Not looking for optimal- I don't expect it from this. I just want to add some snap to my thump.
     
  10. Freddels

    Freddels Musical Anarchist Supporting Member

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    Don't put the mid in the box, make a separate small box to sit on top.
     
  11. topcat2069

    topcat2069 Supporting Member

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    +1
     
  12. topcat2069

    topcat2069 Supporting Member

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    +1 maybe 2 or more mid drivers......
     
  13. wcriley

    wcriley

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    The Alpha6CBMR referenced in the OP is a closed back driver. It doesn't need a seperate box.
     
  14. Freddels

    Freddels Musical Anarchist Supporting Member

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    We're suggesting a separate box so he doesn't cut into his current cab.
     
  15. Foz

    Foz

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    No box needed for the driver OP specified as its a closed back model - but its a pretty crappy choice - so +1 build a mid box, but pick a different speaker to match the box.

    You could build a greenboy style alpha6 headcase to set on top of the Hartke [just copy the mid box dimensions and mid xover design from his 12/6 alpha design]...

    http://greenboy.us/fEARful/headcase.htm

    ... but xover for low passing the woofs would require some thought.

    Best bet might be to just replace the old tweet and add a protective cap? If that gets you what you need then all is sorted - OTOH if/when you are ready a cab to move on to a cab with a real mid driver then my $0.02 = you'd be better off selling the Hartke and starting fresh versus flogging an old horse.
     
  16. Codger

    Codger Supporting Member

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    He's already said he's going to 'break the law'. With the closed back driver he could try it out externally. It would be easier to fiddle with there to adjust a pad to reduce the level for example.

    Here's an 8 ohm 1.6 kHz high-pass.
     
  17. Foz

    Foz

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    You can put a non-crappy driver in an external box just as well...
     
  18. AstroSonic

    AstroSonic Supporting Member

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    It's amazing how much it costs to 'fix' a budget/good buy cabinet. In this case a proper fix with fully symmetrical crossover (HP&LP sections) plus a decent mid driver will cost half or more of what the cab sold for new.It is often times better to simply get the budget cab functional, sell it, then pick up something with more potential.

    A good mid or mids will cost around $100 (or more). The 1.6kHz cover and L-pad will add another $65. The 1.6 to 2 kHz range is a good place to cross to a mid because the 15's are tanking off-axis (well down in level). This minimizes overlap and interaction between the mid and the 15's.

    A lot of people end up really disliking tweeters because they played through cabs with 'budget' tweeters and marginal xovers. A good tweeter can transform the sound of a cab (in a positive sense). It still (probably) leaves a hole in the response between where the 15's (or whatever) drop off and the tweeter comes in, but they do add clarity and snap without being harsh or hissy.
     
  19. Bmorefoozler

    Bmorefoozler

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    The CBG 1212/6 xovwer is 4 ohms/8ohms and available pre-built at speakerhardware.com
    throw that and an 18sound mid in a seperate box and you are good to go.
     
  20. Count Bassie

    Count Bassie Supporting Member

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    I'm liking the separate box idea there, Fred. I can then replace the Hartke down the road, and just get a nice phat little 15 box, or build a 15-only fEArful thing (hah!). That Headcase is a pretty good idea... I might even have a ready box here.

    Thanks for the responses, all! Well-considered stuff to toss around here... so many ways to violate convention...
     
  21. Freddels

    Freddels Musical Anarchist Supporting Member

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    IIRC, 4Mal or Passinwind did a separate box for a mid driver. Do a search and then contact them.
     

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